1. Field of the Invention
This invention relates to external preparations containing, as active ingredients, a placental extract of pregnant cows and kojic acid or a derivative thereof.
2. Description of the Prior Art
Peroxides, such as hydrogen peroxide, magnesium peroxide, sodium peroxide and zinc perborate, had long been used as the active ingredient in the so-called bleach-mask cosmetics, that is, cosmetics to make the human skin fair. But these peroxides, which are very unstable compounds, were poor in storage stability, had difficulty in formulation together with base materials, and were not satisfactory in the intended effect. Cosmetics containing vitamin C, cystein or colloidal sulfur were later introduced for the same purpose, but the effect of these cosmetics was also unsatisfactory. Besides these, are also known bleach-mask cosmetics using kojic acid (Japanese Patent Publication No. 5618569), and bleach-mask cosmetics using kojic acid derivatives (Japanese Patent Kokai No. 56-79616, No. 567710, No. 56-7776 and No. 59-33207). Cosmetics using a placental extract are also known (Japanese Patent Publication No. 35-15399). In addition, bleach-mask cosmetics using a placental extract (from a fullymatured human placenta, for example) and kojic acid or a derivative thereof have also been disclosed (Japanese Patent Kokai No. 61-202806).